Layout.ArticleStack: explicitly destroy children.
Layout.ArticleStack: explicitly destroy children.

To avoid leaking an article content widget (WebkitWebView) each time
we switch to a new one we explicitly destroy the child with child.destroy()
instead of removing it from the hierarchy and relaying on GC. (Which never
happens because we are probably holding a reference in JS)

https://phabricator.endlessm.com/T15913

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib